On 01/02/2011 00:01, Edward Z. Yang wrote:
Current theory:
c1jj: _s1ep::I32 = I32[(slot<_s1ep::I32> + 4)]; // CmmAssign _s1fP::I32 = I32[(slot<_s1fP::I32> + 4)]; // CmmAssign // outOfLine should follow: _s1eq::F64 = F64[_s1fP::I32 + 3]; // CmmAssign I32[(young<c1jh> + 4)] = c1jh; // CmmStore foreign call "ccall" arg hints: [PtrHint,] result hints: [] call_fn_blob(...) returns to c1jh args: ([_s1ep::I32, _s1eq::F64]) ress: ([_s1ev::F64]) with update frame 4; // CmmForeignCall c1jh: _s1ev::F64 = F64[(slot<_s1ev::F64> + 8)]; // CmmAssign // emitReturn: Sequel: Assign _s1ev::F64 = _s1ev::F64; // CmmAssign F64[(slot<_s1ev::F64> + 8)] = _s1ev::F64; // CmmStore goto u1Ak; // CmmBranch
Note the line immediately after c1jh, where we reload the ostensibly spilled _s1ev back into a register. Except that it was never spilled there in the first place, and we just clobbered the real value. Oops.
Is this interpretation correct?
It sounds plausible, but I really have no idea. The code generator does not have to generate spill/reloads around foreign calls, the register allocator will do that. Cheers, Simon